Javascript
Hoisting
Junior

What is the result of following snippet?

What is the result of following snippet?
8
10
SyntaxError
ReferenceError
Javascript
Closure
Junior

What is closure in Javascript?

Javascript
Event loop
Senior

What's the output?

What's the output?
Promise 1! Last line 1! Promise 2! Last line 2! Timeout 1! Timeout 2!
Last line 1! Timeout 1! Promise 1! Last line 2! Promise 2! Timeout 2!
Last line 1! Promise 2! Last line 2! Promise 1! Timeout 1! Timeout 2!
Timeout 1! Promise 1! Last line 1! Promise 2! Timeout 2! Last line 2!
Javascript
Comparison
Intermediate

What is the output?

What is the output?
true false true
false false true
true false false
false true true
Javascript
Declaration
Intermediate

What happens when you run this code?

What happens when you run this code?
It will throw a ReferenceError about x
It will print 18
It will print undefined
It will throw a ReferenceError about y
Javascript
Value
Junior

What does an undefined value stand for?

undefined value indicate for the absence of an value
undefined value indicate for the absence of an object
undefined value indicate for the absence of an array
undefined value indicate for the absence of an falsy value
Javascript
Value
Junior

What is null value stand for?

null value indicate for the absence of an value
null value indicate for the absence of an object
null value indicate for the absence of an array
null value indicate for the absence of an falsy value
Javascript
Value
Junior

What is NaN value stand for?

NaN value indicate that value can not present in number
NaN value indicate that value is too big
NaN value indicate that value is not existed
NaN value indicate that value is too small
Javascript
Value
Junior

What is Symbol value?

Symbol is a kind of number value and share same number properties
Symbol value is not existed in Javascript
Symbol is unique and immutable primitive value in Javascript
Symbol is a kind of string value and share same string properties
Javascript
this
Intermediate

What's the output

What's the output
20 and 62.83185307179586
20 and NaN
20 and 63
NaN and 63